1. Field of the Invention:
This invention relates to a method of cleaning the bottom of a channel for feeding fish and an apparatus thereof and, more particularly to a method and an apparatus suitable for cleaning the bottom of a feeding channel for fry of salmon, trout or the like.
2. Description of the Background Art:
The incubation of salmon and trout such as pink salmon, masou salmon, trout, char and like fish usually comprises a breeding step, in which fertilized eggs are bred, a repose period control step for controlling a repose period of yoke sac fry in an incubation channel where fresh water flows at all time, and a feed step, in which free swimming fry in a free swimming period after the repose period is fed in a feeding channel where fresh water flows at all time.
A feeding channel having substantially the flat bottom free from the inclination is used for feeding of free swimming fry. The feeding channel is supplied fresh water at all time such as to maintain the flow of water in said channel to a predetermined velocity. The grown free swimming fry is transferred from the incubation channel to said feeding channel and further the bait for the free swimming fry is sprayed over said channel.
The feeding channel may be used as the incubation channel. In this case, a member, i.e., gravels disposed in the incubation channel in order to provide a repose place for the yolk sac fry is removed from the incubation channel.
A deposit forms on the bottom of the feeding channel which is precipitated by the resisual of the bait sprayed therein, excrements of fish and mud or the like. The deposit noted above is widely distributed over the entire surface of the bottom and flows up through the water to disperse therethrough. In this case, the water is liable to contaminate. When the deposit is left on the bottom as it is, corrosion of said deposit produces the pathogenic bacteria of fish and fur or the like, thereby rapidly contaminating the inside of the feeding channel and is liably to produce fish deseases and oxegen starvation or the like. As a result, it has been desired that the feeding channel should be cleaned by entirely removing the deposit produced over the entire surface of the bottom of channel as frequently as possible, i.e., every day or every few days.
One of an apparatus for cleaning the bottom of the feeding channel has been disclosed in which a cleaner enters the channel to withdraw the deposit by using an elongate pipe and a suction pump. However, the apparatus noted above is liable to suck up fry on the bottom even when the suction force of the suction pump is reduced. Further, according to the apparatus, an end of said pipe should be moved by hand slowly along the bottom of the channel while paying attention so as not to disturb the deposit through the water. Therefore, it takes much time for cleaning and is substantially impossible to clean each bottom of a plurality of feeding channels every day or every one or other day. As a result, from the practical point of view, the apparatus noted above is merely used for occasionally removing the deposit which is locally collected on the bottom of the feeding channel and is clearly visible to the eye.
Thus, there has been developed up to now an apparatus for removing efficiently and economically the deposit which is liable to disturbed through water from the bottom and widely distributed over the entire surface of the bottom without contaminating the channel even when the deposit is dispersed through the water and damaging the fry. Therefore, only the occasional removal of the deposit which particularly leaps to the eye has been conventionally performed. The entire surface of the bottom of the feeding channel has not been cleaned during the feeding period of fry but cleaned after said period.